Java Spring Boot - enable xml declaration tag

InterceptorConfig.java

@Configuration
public class InterceptorConfig implements WebMvcConfigurer {

    @Bean
    public MappingJackson2XmlHttpMessageConverter mappingJackson2XmlHttpMessageConverter(
            Jackson2ObjectMapperBuilder builder) {
        ObjectMapper mapper = builder.createXmlMapper(true).build();
        ((XmlMapper) mapper).enable(ToXmlGenerator.Feature.WRITE_XML_DECLARATION);
        return new MappingJackson2XmlHttpMessageConverter(mapper);
    }
}